There are many opinions on buffing speed in the various instructionals on the web, but they all contain a fallacy. They use 8" wheels and give the speed in RPM, but the actual effective speed, as one is buffing on the periphery of the wheel or bowl buff, is feet per minute (FPM). Different sized wheels at the same RPM have very different effective speeds in FPM. I got into this dilemma as I use 8" and 4" wheels as well as a couple of sizes of bowl buffs.
I make no pretense of being an expert in the best buffing speed, and it probably varies with the finish and the compound and personal taste. But that speed in RPM varies with the size of the wheel or bowl buff. A sudden remembrance of my high school geometry made me realize that one can easily figure the RPM for a desired FPM as one changes wheels. Good old Pi x D gives us the circumference of the wheel. For example, an 8" wheel has a circumference of 25" and a 4" wheel is 12.5". If you like 1000 RPM with an 8" wheel then you will like 2000 RPM with a 4" wheel. A 6" wheel is 18.8" around, and a 2" bowl buff 6.3" around, but that is too detailed - lets just make them 18.75" and 6.25" so that we have a nice straight line graph.
I'll use 1000 RPM as it is an easy number, I prefer a higher RPM for my 8" wheels. That gives us 25,000 inches per minute, or 2083 FPM. A 4" wheel at 2000 RPM also gives us 2083 FPM. If the 6" wheel circumference were actually 18.75" then 1500 RPM would also give 2083 FPM (18.75 is close enough to the actual 18.8 to just use the factor).
I might point out that the same consideration applies to turning and sanding. The recommendations for turning speeds (rough and finish) in your lathe instructions are the same principle, it is the speed of the surface of the wood against the tool in FPM that is the criterion.
I make no pretense of being an expert in the best buffing speed, and it probably varies with the finish and the compound and personal taste. But that speed in RPM varies with the size of the wheel or bowl buff. A sudden remembrance of my high school geometry made me realize that one can easily figure the RPM for a desired FPM as one changes wheels. Good old Pi x D gives us the circumference of the wheel. For example, an 8" wheel has a circumference of 25" and a 4" wheel is 12.5". If you like 1000 RPM with an 8" wheel then you will like 2000 RPM with a 4" wheel. A 6" wheel is 18.8" around, and a 2" bowl buff 6.3" around, but that is too detailed - lets just make them 18.75" and 6.25" so that we have a nice straight line graph.
I'll use 1000 RPM as it is an easy number, I prefer a higher RPM for my 8" wheels. That gives us 25,000 inches per minute, or 2083 FPM. A 4" wheel at 2000 RPM also gives us 2083 FPM. If the 6" wheel circumference were actually 18.75" then 1500 RPM would also give 2083 FPM (18.75 is close enough to the actual 18.8 to just use the factor).
I might point out that the same consideration applies to turning and sanding. The recommendations for turning speeds (rough and finish) in your lathe instructions are the same principle, it is the speed of the surface of the wood against the tool in FPM that is the criterion.